Fix key frame detection
Fix key frame detection

This solves the regression issue seen in certain animation clips.

BUG=b/132108583

Change-Id: Ib28413c95160a5f15fbcf9ea6a322fd4f69a57ce

webmproject/libvpx,ShiftMediaProject/libvpx,ShiftMediaProject/libvpx,webmproject/libvpx,webmproject/libvpx,webmproject/libvpx,ShiftMediaProject/libvpx,webmproject/libvpx,ShiftMediaProject/libvpx,ShiftMediaProject/libvpx,webmproject/libvpx